diff --git a/src/index.tsx b/src/index.tsx
index 884c5f3..132e1dd 100644
--- a/src/index.tsx
+++ b/src/index.tsx
@@ -216,4 +216,5 @@ export function define(nameOrDef: string | TagDef, defIfNamed?: TagDef) {
   }
 }
 
+// shortcut so you only have to import one thing, if you want
 define.Styles = Styles
\ No newline at end of file
diff --git a/src/tests/index.test.tsx b/src/tests/index.test.tsx
index 9a130c6..486c098 100644
--- a/src/tests/index.test.tsx
+++ b/src/tests/index.test.tsx
@@ -744,6 +744,147 @@ describe('variants on parts via props', () => {
   })
 })
 
+describe('base with attributes', () => {
+  test('extracts element name from base with attributes', () => {
+    const Component = define('InputRadio', {
+      base: 'input[type=radio]',
+      display: 'block'
+    })
+
+    const html = renderToString(Component({}))
+    expect(html).toContain('<input')
+    expect(html).toContain('type="radio"')
+    expect(html).toContain('class="InputRadio"')
+  })
+
+  test('extracts multiple attribute formats', () => {
+    const Component = define('InputCheckbox', {
+      base: 'input[type=checkbox]'
+    })
+
+    const html = renderToString(Component({}))
+    expect(html).toContain('type="checkbox"')
+  })
+
+  test('works without attributes', () => {
+    const Component = define('PlainInput', {
+      base: 'input',
+      padding: 10
+    })
+
+    const html = renderToString(Component({}))
+    expect(html).toContain('<input')
+    expect(html).not.toContain('type=')
+  })
+
+  test('base attributes can be overridden by props', () => {
+    const Component = define('OverridableInput', {
+      base: 'input[type=text]'
+    })
+
+    const html = renderToString(Component({ type: 'email' }))
+    expect(html).toContain('type="email"')
+  })
+})
+
+describe('selectors with @ and &', () => {
+  test('generates CSS for selectors with @PartName', () => {
+    define('SelectorTest', {
+      parts: {
+        Input: { base: 'input[type=checkbox]', display: 'none' },
+        Label: {
+          base: 'label',
+          color: '#666',
+          selectors: {
+            '@Input:checked + &': {
+              color: 'blue'
+            }
+          }
+        }
+      }
+    })
+
+    const css = getStylesCSS()
+    expect(css).toContain('.SelectorTest_Input:checked + .SelectorTest_Label')
+    expect(css).toContain('color: blue')
+  })
+
+  test('selectors support general sibling combinator ~', () => {
+    define('SiblingTest', {
+      parts: {
+        Trigger: { base: 'input[type=checkbox]' },
+        Content: {
+          display: 'none',
+          selectors: {
+            '@Trigger:checked ~ &': {
+              display: 'block'
+            }
+          }
+        }
+      }
+    })
+
+    const css = getStylesCSS()
+    expect(css).toContain('.SiblingTest_Trigger:checked ~ .SiblingTest_Content')
+    expect(css).toContain('display: block')
+  })
+
+  test('selectors can include pseudo-classes on &', () => {
+    define('PseudoTest', {
+      parts: {
+        Radio: { base: 'input[type=radio]', display: 'none' },
+        Label: {
+          base: 'label',
+          selectors: {
+            '@Radio:checked + &:hover': {
+              background: 'lightblue'
+            }
+          }
+        }
+      }
+    })
+
+    const css = getStylesCSS()
+    expect(css).toContain('.PseudoTest_Radio:checked + .PseudoTest_Label:hover')
+    expect(css).toContain('background: lightblue')
+  })
+
+  test('selectors work on root level', () => {
+    define('RootSelectorTest', {
+      color: 'black',
+      selectors: {
+        '&:hover': {
+          color: 'blue'
+        }
+      }
+    })
+
+    const css = getStylesCSS()
+    expect(css).toContain('.RootSelectorTest:hover')
+    expect(css).toContain('color: blue')
+  })
+
+  test('supports multiple selectors', () => {
+    define('MultiSelectorTest', {
+      parts: {
+        Input: { base: 'input[type=checkbox]' },
+        Label: {
+          selectors: {
+            '@Input:checked + &': { color: 'green' },
+            '@Input:disabled + &': { opacity: 0.5 }
+          }
+        }
+      }
+    })
+
+    const css = getStylesCSS()
+    expect(css).toContain('.MultiSelectorTest_Input:checked + .MultiSelectorTest_Label')
+    expect(css).toContain('color: green')
+    expect(css).toContain('.MultiSelectorTest_Input:disabled + .MultiSelectorTest_Label')
+    expect(css).toContain('opacity: 0.5')
+  })
+})
+
 describe('edge cases', () => {
   test('handles empty definition', () => {
     const Component = define({})
@@ -777,13 +918,12 @@ describe('edge cases', () => {
     expect(html).toContain('size-small')
   })
 
-  test('does not duplicate styles when registered multiple times', () => {
-    define('NoDuplicate', { width: 100 })
-    define('NoDuplicate', { width: 200 })
+  test('throws error when defining duplicate component names', () => {
+    define('NoDuplicateTest', { width: 100 })
 
-    const styles = parseCSS(getStylesCSS())
-    // Should keep first value (??= operator)
-    expect(styles['NoDuplicate']?.['width']).toBe('100px')
+    expect(() => {
+      define('NoDuplicateTest', { width: 200 })
+    }).toThrow('NoDuplicateTest is already defined! Must use unique names.')
   })
 
   test('handles complex nested structures', () => {